This application claims the benefit of a Japanese Patent Application No. 2001-163254 filed May 30, 2001, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to tracking control methods and storage apparatuses, and more particularly to a tracking control method for recording and/or reproducing information with respect to an optical recording medium with a desired recording and/or reproducing margin, and to a storage medium which employs such a tracking control method.
In magneto-optical disk units, there are magneto-optical disk units which record and/or reproduce information with respect to a land of the magneto-optical disk, and there are magneto-optical disk units which record and/or reproduce information with respect to both a land and a groove of the magneto-optical disk. By employing the so-called land-groove recording system which records and/or reproduces information with respect to both the land and the groove of the magneto-optical disk, it is possible to increase the recording density on the magneto-optical disk.
2. Description of the Related Art
In an optical recording medium, typified by the magneto-optical disk, which has a narrow track pitch and employs the land-groove recording system, there is a possibility that a signal reproducing performance of a target track will be deteriorated by signal interference from signals written on tracks adjacent to the target track.
It is known that one cause of the signal interference at the time of the reproduction is a radial tilt, that is, an inclination of an optical axis in a radial direction with respect to a recording surface (reflection surface) of the optical recording medium. When the radial tilt exists, aberration is generated in a light beam, and a reproduced signal becomes easily affected by the interference of the signals from the adjacent tracks. Normally, in a state where the radial tilt is small, a center of a tracking error signal (TES) becomes a minimum point of a read error rate, and thus, a tracking target position need only be set to the center of the TES. On the other hand, in a state where the radial tilt is large, it is known that the minimum point of the read error rate is a point where the tracking target position is shifted in one direction from the center of the TES.
The track pitch of the conventional optical recording medium is relatively large. For this reason, it is possible to obtain a sufficient recording and/or reproducing margin even if the tracking target position is set to the center of the TES. However, as the storage capacity of the optical recording medium increases and the track pitch is reduced, it may be anticipated that the effects of the radial tilt will further increase.
As a means of solving these problems, proposals have been made on a tilt correcting mechanism which mechanically corrects the relative position and angle between an optical head and the optical recording medium. But when a new mechanism such as the tilt correcting mechanism is added to the existing structure of the storage apparatus, both the structure and control of the storage apparatus become complex, and the storage apparatus becomes expensive.
Therefore, the effects of the radial tilt become more conspicuous as the track pitch of the optical recording medium is further reduced, and there is a problem in that the recording and/or reproducing margin of the conventional storage apparatus may become considerably deteriorated. In addition, there is a problem in that providing the tilt correcting mechanism will make both the structure and control of the storage apparatus complex and also make the storage apparatus expensive.